1. Field of the Invention
The present invention relates to a method of manufacture for a semiconductor device, particularly a method of stabilizing surface properties of a material layer.
2. Description of the Related Art
Film deposition is one of the important steps in semiconductor device fabrication process. Generally, a semiconductor device is constituted from a plurality of layers (material layers) of films of various thickness. The stability of these films (material layers) will affect the performance of the semiconductor device. Therefore, in semiconductor fabrication process, how to stabilize the surface properties of the material layers is important.
For instance, in general, in the process of depositing material layers, a plurality of wafers are stacked and placed in a Front Opening Unified Pod, FOUP. A robot arm is used to take the wafers, in sequence, from the FOUP and transfer the wafers to a chamber to proceed with the deposition of the material layers. After that the wafers having been deposited with material layers are delivered to the FOUP again. Since the FOUP is under normal pressure, when the first wafer is transferred back to the FOUP, the wafer is transferred from an almost vacuum environment to that of atmospheric pressure, and the film surface will oxidize with oxygen within the atmosphere. This oxidation reaction will increase the resistance value of the wafer. Further, the extent of oxidation of each wafer is different with respect to duration of storage. In other words, the surface properties of the material layer on the first wafer will be different from that of the last wafer. Such a difference affects the subsequent fabrication process to a certain extent, and consequently the yield and stability of the semiconductor device will be affected.
Besides, when the wafer deposited with material layers is placed in the FOUP for storage, the residual gas will be released from the wafer surface (known as outgassing). This gas dispersed from the wafer will contaminate the untreated wafer surface. When these contaminated wafers proceed to material layer deposition, the material layer possesses the original material and the contaminant adhered onto the wafer. Thus, the yield of product will be lowered. Accordingly, it is an object of the present invention to provide a method of stabilizing surface properties of the material layer and at the same time lowering contamination of wafer caused by outgassing.